Noun, する verb, and の adjective
そんざい
そもそも、この町には水害防止対さくが存在していなかったんだよ。
There were no existing flood-control measures in this town to begin with.
じゃあ、最初はオゾンそうに穴は存在していなかったんですか？
So does that mean there were no holes in the ozone layer originally?
「コウイチさんが存在するとは思えない…」とフグは言った。
"I can’t believe Koichi exists..." Fugu said.
I exist, I suppose... this is the kind of existence I have. I'm not really sure either way, and I don't care. Existence is futile, I suppose.
This is a jukugo word, which usually means on'yomi readings from the kanji. If you know the readings of your kanji you'll know how to read this as well.